This invention relates to spirooxazine photochromic compounds having a particular utility in fabricating photochromic sunglass lenses and the like.
1,3,3-trimethylspiro.vertline.indoline-2,3'-.vertline.3H.vertline.naphth-.v ertline.2,1-b.vertline. (1,4) oxazines.vertline. are known photochromic compounds. The change in optical density between the unactivated and activated states as measured at the wavelength of maximum absorption ranges from about 0.43 to about 0.89 for some of the disclosed species. Such compounds are disclosed in U.S. Pat. No. 3,578,602 to Ono et al, entitled "Photochromic Compound". Another Ono et al U.S. Pat. No. 3,562,172 discloses similar compounds.